This invention pertains to electronic clock regulating apparatus and more particularly to such apparatus of the time interval rate meter type.
In the prior art, two general methods have been used for regulating clocks and watches. The first such method involves counting the number of clock ticks or clock pulses generated by the clock for a specified length of time which may be termed "the measurement interval". The second such method has involved measuring very accurately the time interval elapsing between clock ticks or pulses from the clock being regulating.
The first of the above methods give a count which is directly proportional to the clock rate. However, where this rate is relatively slow, a very long sampling time interval may be needed to obtain the desired accuracy for regulation of the clock. In the second method, the count which is generated is inversely proportional to the rate of the clock being regulated. This technique, however, has the additional advantage that a high degree of accuracy may be obtained over a relatively short sampling time or measurement time interval.
Prior art commercial clock and watch regulating devices such as that shown in U.S. Pat. No. 3,811,314, have generally employed fixed predetermined sampling time intervals which are related to the gear train ratios commonly used in certain types of commercial clocks and watches. For example, in conventional clocks and watches, the mainly used frequencies are 3,600; 16,000; 17,280; 18,000; 19,200; 19,800; 36,000; and 72,000 beats per hour. In the case of certain tuning fork type watches, frequencies such as 360 cycles per second and 200 and 300 cycles per second are also commonly used. The measurement or sampling time interval (which may be termed the "ideal period") in these type prior art clock regulators has been limited to periods specified by these particular commercially used gear train or tuning fork frequencies.
In dealing with antique clocks and watches, however, commonly used present day commercial gear ratios or tuning fork frequencies may not be commonly encountered. A need has arisen, therefore, for a clock regulator which is capable of determining the error of such a clock or watch from an idealized period and which may be continuously varied over a relatively wide range of such idealized periods or time intervals. The present invention has much more flexibility than prior art devices of the type in the aforementioned patent, in that it provides a time interval rate meter which is capable of accurately measuring the time interval between the clock ticks or clock pulses of a clock being regulated. The regulator of the present invention displays in a desired format the error from the idealized period which may be varied over a range of 10.sup.7. The present invention thus has a much wider range of applicability than prior art devices. Similarly, the present invention by employing totally electronic and digital logic avoids many of the cumbersome and mechanically troublesome features present in prior art electromechanical clock regulators.
The clock regulator of the present invention permits measurement of a clock's error to within a few one thousandths of a second to be accomplished within only a few minutes of adjustment interval. Roughing in adjustments on a clock are performed very quickly with this instrument because gross errors in time keeping are revealed in just four or five swings of the clock pendulum or balance wheel. Utilizing the clock regulator of the present invention, regulation of a clock to within one minute per day usually occupies less than five minutes of a technician's time. Regulation to within ten seconds per day can be accomplished by making test runs of two minutes duration. Higher degrees of accuracy may be obtained by employing longer test periods. Utilizing the clock regulator of the present invention, other factors concerning a clock's operation may be discerned by the skilled technician. Variations of the clock's rate are immediately revealed by the regulator and can be correlated with clock defects such as irregular or out of round wheels, binding of a wheel and defects due to variation of main spring tension in the clock. Regulation of a clock by use of the present invention is performed by presetting the regulator to the idealized cyclic time period which is produced by the mechanical clock to be regulated and which would result in extremely accurate timekeeping. This presetable cyclic time period or idealized time period is continuously adjustable in the clock regulator of the present invention from 0.000001 seconds to 9.999999 seconds in one microsecond steps. The regulator is coupled to the clock by a contact microphone pickup device and is then synchronized to the clock tick rate. The out-of-adjustment or non-ideal characteristics of the clock being regulated results in a gradual loss of this synchronism. This loss of synchronism is measured by the regulator circuitry which displays this drift or error on a display means calibrated in convenient units. The clock technician may then use the measured drift to estimate or calculate necessary corrections to the mechanical clock. When these corrections are performed, another test using the regulator is initiated. This procedure may be repeated until a desired degree of accuracy is achieved.